This invention relates to surface illuminators, and more particularly to a dark field multi-directional surface illuminator of the type which is particularly suitable for illuminating objects that are being inspected by contour projectors, optical comparators, microscopes, and similar inspection systems.
Proper illumination of an object is most important when its image is to be magnified and observed by the lens system of a contour projector, optical comparator, microscope, or the like. There are many known devices for illuminating such objects, but one disadvantage is that for most such devices the illuminating light usually originates from a single source and is directed along a single path onto the object. Moreover, there frequently is an overlapping or at least partial coincidence of the path of light, which is used for illuminating the object, with the path of the image which is projected to the observer's eye, therefore creating at least some interference with the projected image.
When properly controlled, oblique illumination often enhances the edges of features on an observed object of the type described, particularly when the illuminating light is oriented in a direction most perpendicular to a respective edge. This has been found to be particularly true where it is possible to vary the intensity of the illuminating light.
Accordingly, it is an object of this invention to provide an improved, relatively inexpensive and extremely efficient multi-directional surface illuminator, which is designed to illuminate with variable intensity predetermined, selected surfaces on an object which is being observed in an inspection system of the type described.
Another object of this invention is to provide an illuminator of the type described which is of the dark field, multi-directional variety, and which is capable of illuminating selected surfaces of an object without interfering with the imaging path of the system.
A more specific object of this invention is to provide an improved multi-directional illuminator in which light from four individually controllable light sources is projected along four quadrants onto a single condenser lens, which focuses the light obliquely onto the surface of an object which is to be inspected.
Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.